Malaria Ag Research Articles

Comparison of Malaria Rapid Diagnostic Test Kit and Microscopy

Malaria is the most common single diagnosis made in many countries in Africa. Microscopy is the gold standard for laboratory diagnosis of malaria parasite, but it requires adequate training and the time to get results is longer than that for Rapid Diagnostic Tests (RDTs). Use of RDTs is an alternative diagnostic method. This method is quick and easy to carry out. This study examined 412 blood samples of patients who met the study inclusion criteria from the health centres. All of the samples obtained were tested by SD Bioline malaria Ag P.f test commonly available in Nigeria and parasite count was done from thick film prepared. The results obtained were presented as a proportion positive in comparison to the total number of participants enrolled. Of the 412 enrollees, 284 were tested positive with malaria using the RDT, 400 were tested positive with microscopy and 12 were negative using microscopy and RDT. This study confirms the superior sensitivity of microscopy to RDTs in diagnosis of malaria. Although RDTs are very useful for quick diagnosis of malaria, particularly in areas where access to the use of microscopy is not available, the possibility of a low performance by RDTs in malaria diagnosis should be emphasized on health practitioners and microcopy should be encouraged as much as possible.

A new highly sensitive enzyme-linked immunosorbent assay for the detection of Plasmodium falciparum histidine-rich protein 2 in whole blood

BackgroundThe detection of submicroscopic infections in low prevalence settings has become an increasingly important challenge for malaria elimination strategies. The current field rapid diagnostic tests (RDTs) for Plasmodium falciparum malaria are inadequate to detect low-density infections. Therefore, there is a need to develop more sensitive field diagnostic tools. In parallel, a highly sensitive laboratory reference assay will be essential to evaluate new diagnostic tools. Recently, the highly sensitive Alere™ Malaria Ag P.f ELISA (HS ELISA) was developed to detect P. falciparum histidine-rich protein 2 (HRP2) in clinical whole blood specimens. In this study, the analytical and clinical performance of the HS ELISA was determined using recombinant P. falciparum HRP2, P. falciparum native culture parasites, and archived highly pedigreed clinical whole blood specimens from Karen village, Myanmar and Nagongera, Uganda.ResultsThe HS ELISA has an analytical sensitivity of less than 25 pg/mL and shows strong specificity for P. falciparum HRP2 when tested against P. falciparum native culture strains with pfhrp2 and pfhrp3 gene deletions. Additionally, the Z′-factor statistic of 0.862 indicates the HS ELISA as an excellent, reproducible assay, and the coefficients of variation for inter- and intra-plate testing, 11.76% and 2.51%, were acceptable. Against clinical whole blood specimens with concordant microscopic and PCR results, the HS ELISA showed 100% (95% CI 96.4–100) diagnostic sensitivity and 97.9% (95% CI 94.8–99.4) diagnostic specificity. For P. falciparum positive specimens with HRP2 concentrations below 400 pg/mL, the sensitivity and specificity were 100% (95% CI 88.4–100) and 88.9% (95% CI 70.8–97.6), respectively. The overall sensitivity and specificity for all 352 samples were 100% (CI 95% 96–100%) and 97.3% (CI 95% 94–99%).ConclusionsThe HS ELISA is a robust and reproducible assay. The findings suggest that the HS ELISA may be a useful tool as an affordable reference assay for new ultra-sensitive HRP2-based RDTs.

Performance of an ultra-sensitive Plasmodium falciparum HRP2-based rapid diagnostic test with recombinant HRP2, culture parasites, and archived whole blood samples

BackgroundAs malaria endemic countries shift from control to elimination, the proportion of low density Plasmodium falciparum infections increases. Current field diagnostic tools, such as microscopy and rapid diagnostic tests (RDT), with detection limits of approximately 100–200 parasites/µL (p/µL) and 800–1000 pg/mL histidine-rich protein 2 (HRP2), respectively, are unable to detect these infections. A novel ultra-sensitive HRP2-based Alere™ Malaria Ag P.f RDT (uRDT) was evaluated in laboratory conditions to define the test’s performance against recombinant HRP2 and native cultured parasites.ResultsThe uRDT detected dilutions of P. falciparum recombinant GST-W2 and FliS-W2, as well as cultured W2 and ITG, diluted in whole blood down to 10–40 pg/mL HRP2, depending on the protein tested. uRDT specificity was 100% against 123 archived frozen whole blood samples. Rapid test cross-reactivity with HRP3 was investigated using pfhrp2 gene deletion strains D10 and Dd2, pfhrp3 gene deletion strain HB3, and controls pfhrp2 and pfhrp3 double deletion strain 3BD5 and pfhrp2 and pfhrp3 competent strain ITG. The commercial Standard Diagnostics, Inc. BIOLINE Malaria Ag P.f RDT (SD-RDT) and uRDT detected pfhrp2 positive strains down to 49 and 3.13 p/µL, respectively. The pfhrp2 deletion strains were detected down to 98 p/µL by both tests.ConclusionThe performance of the uRDT was variable depending on the protein, but overall showed a greater than 10-fold improvement over the SD-RDT. The uRDT also exhibited excellent specificity and showed the same cross-reactivity with HRP3 as the SD-RDT. Together, the results support the uRDT as a more sensitive HRP2 test that could be a potentially effective tool in elimination campaigns. Further clinical evaluations for this purpose are merited.

Insights into the Performance of SD Bioline Malaria Ag P.f/Pan Rapid Diagnostic Test and Plasmodium falciparum Histidine-Rich Protein 2 Gene Variation in Madagascar.

Plasmodium falciparum histidine-rich protein 2 (PfHRP2) forms the basis of many current malaria rapid diagnostic tests (RDTs). However, the parasites lacking part or all of the pfhrp2 gene do not express the PfHRP2 protein and are, therefore, not identifiable by PfHRP2-detecting RDTs. We evaluated the performance of the SD Bioline Malaria Ag P.f/Pan RDT together with pfhrp2 variation in Madagascar. Genomic DNA isolated from 260 patient blood samples were polymerase chain reaction (PCR)-amplified for the parasite 18S rRNA and pfhrp2 genes. Post-PCR ligation detection reaction-fluorescent microsphere assay (LDR-FMA) was performed for the identification of parasite species. Plasmodium falciparum histidine-rich protein 2 amplicons were sequenced. Polymerase chain reaction diagnosis of patient samples showed that 29% (75/260) were infected and P. falciparum was present in 95% (71/75) of these PCR-positive samples. Comparing RDT and P. falciparum detection by LDR-FMA, eight samples were RDT negative but P. falciparum positive (false negatives), all of which were pfhrp2 positive. The sensitivity and specificity of the RDT were 87% and 90%, respectively. Seventy-three samples were amplified for pfhrp2, from which nine randomly selected amplicons were sequenced, yielding 13 sequences. Amplification of pfhrp2, combined with RDT analysis and P. falciparum detection by LDR-FMA, showed that there was no indication of pfhrp2 deletion. Sequence analysis of pfhrp2 showed that the correlation between pfhrp2 sequence structure and RDT detection rates was unclear. Although the observed absence of pfhrp2 deletion from the samples screened here is encouraging, continued monitoring of the efficacy of the SD Bioline Malaria Ag P.f/Pan RDT for malaria diagnosis in Madagascar is warranted.

Plasmodium falciparum diagnostic tools in HIV-positive under-5-year-olds in two ART clinics in Ghana: are there missed infections?

BackgroundPlasmodium falciparum, the most dominant species in sub-Saharan Africa, causes the most severe clinical malaria manifestations. In resource-limited Ghana, where malaria and HIV geographically overlap, histidine-rich protein 2 (HRP2)-based rapid diagnostic test (RDT) is a faster, easier and cheaper alternative to clinical gold standard light microscopy. However, mutations in parasite hrp2 gene may result in missed infections, which have severe implications for malaria control.MethodsThe performance of a common HRP2-based RDT and expert light microscopy in HIV-positive and HIV-negative children under 5 years old was compared with PCR as laboratory gold standard. Finger-prick capillary blood was tested with First Response® Malaria Ag P. falciparum (HRP2). Giemsa-stained thick and thin blood films were examined with ≥ 200 high power fields and parasites counted per 200 white blood cells. Nested PCR species identification of P. falciparum was performed and resolved on agarose gel. False negatives from RDT were further tested for deleted pfhrp2/3 and flanking genes, using PCR. The study was performed in two anti-retroviral therapy clinics in Accra and Atibie.ResultsOut of 401 participants enrolled, 150 were HIV positive and 251 HIV negative. Malaria was more prevalent in children without HIV. Microscopy had a higher sensitivity [100% (99–100)] than RDT [83% (53.5–100)]. Parasites with pfhrp2/3 deletions contributed to missed infections from RDT false negatives.ConclusionCirculation of malaria parasites with pfrhp2/3 deletions in this population played a role in missed infections with RDT. This ought to be addressed if further strides in malaria control are to be made.

Rapid diagnostic test versus microscopy in the diagnosis of acute malaria in a district hospital in Enugu state, Southeast Nigeria

Background: Malaria is a systemic disease caused by various species of Plasmodium, transmitted through the bite of a female Anopheles mosquito. According to the World Health Organisation, there were 214 million cases of malaria worldwide in 2015. Nigeria’s burden of malaria is about 51million cases and 207,000 deaths annually, accounting for 60% of outpatient visits to hospitals, 11% of maternal mortality, and 30% of child mortality. The study aimed to compare RDT and microscopy in malaria diagnosis in a District Hospital in Enugu state, Southeast Nigeria. Methods: Blood samples of 300 suspected cases of acute malaria were tested for malaria parasite using RDT and microscopy simultaneously. Results: In 2017, the study found a malaria prevalence of 25% (46.2% in children, and 18.1% in adults) in Awgu. RDT was positive in 38% and microscopy in 70.3% of cases. Both RDT and microscopy were positive in 36.3%, negative in 28.3%, and discordant in 35.4%. Sensitivity of RDT was 50.7% (89.4% in children, and 25.6% in adults). RDT had a specificity of 100% (both children and adults), positive predictive value of 1 (both children and adults), and negative predictive value of 0.6 (0.5 in children, 0.6 in adults). Conclusions: RDT (SD Malaria Ag P. f) had more sensitivity in children (89.4%) than adults (25.6%), and the occurrence of false negative results was more in adults (46.8%) than children (9.5%). All negative RDT results need to be examined microscopically, to rule out false negative cases.

Evaluation of the Deki Reader\u2122, an automated RDT reader and data management device, in a household survey setting in low malaria endemic southwestern Uganda

BackgroundEarly diagnosis of suspected malaria cases with a rapid diagnostic test (RDT) has been shown to be an effective malaria control tool used in many resource-constrained settings. However, poor quality control and quality assurance hinder the accurate reporting of malaria diagnoses. Recent use of a portable, battery operated RDT reader (Deki Reader™, Fio Corporation) has shown to have high agreement with visual inspection across diverse health centre settings, however evidence of its feasibility and usability during cross sectional surveys are limited. This study aimed to evaluate the performance of the Deki Reader™ in a cross-sectional survey of children from southwestern Uganda.MethodsA two-stage, stratified cluster sampling survey was conducted between July and October 2014 in three districts of southwestern Uganda, with varying malaria transmission intensities. A total of 566 children aged 6–59 months were included in the analysis. Blood samples were collected and tested for malaria using: the SD Bioline Malaria Ag Pf/Pan RDT and microscopy. Results were compared between visual inspection of the RDT and by the Deki Reader™. Diagnostic performance of both methods were compared to gold-standard microscopy.ResultsThe sensitivity and specificity of the Deki Reader™ was 94.1% (95% CI 69.2–99.6%) and 95.6% (95% CI 93.4–97.1%), respectively. The overall percent agreement between the Deki Reader™ and visual RDT inspection was 98.9% (95% CI 93.2–99.8), with kappa statistic of 0.92 (95% CI 0.85–0.98).ConclusionsThe findings from this study suggest that the Deki Reader™ is comparable to visual inspection and performs well in detecting microscopy-positive Plasmodium falciparum cases in a household survey setting. However, the reader’s performance was highly dependent on ensuring adequate battery life and a work environment free of dirt particles.

Performance of a High-Sensitivity Rapid Diagnostic Test for Plasmodium falciparum Malaria in Asymptomatic Individuals from Uganda and Myanmar and Naive Human Challenge Infections.

.Sensitive field-deployable diagnostic tests can assist malaria programs in achieving elimination. The performance of a new Alere™ Malaria Ag P.f Ultra Sensitive rapid diagnostic test (uRDT) was compared with the currently available SD Bioline Malaria Ag P.f RDT in blood specimens from asymptomatic individuals in Nagongera, Uganda, and in a Karen Village, Myanmar, representative of high- and low-transmission areas, respectively, as well as in pretreatment specimens from study participants from four Plasmodium falciparum-induced blood-stage malaria (IBSM) studies. A quantitative reverse transcription PCR (qRT-PCR) and a highly sensitive enzyme-linked immunosorbent assay (ELISA) test for histidine-rich protein II (HRP2) were used as reference assays. The uRDT showed a greater than 10-fold lower limit of detection for HRP2 compared with the RDT. The sensitivity of the uRDT was 84% and 44% against qRT-PCR in Uganda and Myanmar, respectively, and that of the RDT was 62% and 0% for the same two sites. The specificities of the uRDT were 92% and 99.8% against qRT-PCR for Uganda and Myanmar, respectively, and 99% and 99.8% against the HRP2 reference ELISA. The RDT had specificities of 95% and 100% against qRT-PCR for Uganda and Myanmar, respectively, and 96% and 100% against the HRP2 reference ELISA. The uRDT detected new infections in IBSM study participants 1.5 days sooner than the RDT. The uRDT has the same workflow as currently available RDTs, but improved performance characteristics to identify asymptomatic malaria infections. The uRDT may be a useful tool for malaria elimination strategies.

RE-EVALUATION OF MALARIA DIAGNOSIS BY MOLECULAR METHODS REVEALS MUTATIONS IN HRP-2 AND DRUG RESISTANCE MARKERS IN CAMEROON

BackgroundAs the decline in malaria cases becomes obvious in most sub-Saharan African countries, a new major concern is accurate diagnosis of low parasitaemia which can cause sub-patent infections and false-negative...

Prevalence of <i>Plasmodium</i> Species Infection Among Private Security Guards in Kaduna Metropolis, Kaduna State-Nigeria

Private security guards play an important role in providing security to the citizenry especially in a developing country like Nigeria. They are however many at times exposed to vector borne diseases such as malaria. To determine the prevalence of Plasmodium species infections among private security guards in Kaduna metropolis, Kaduna-Nigeria, two hundred and sixty-one (261) blood samples were collected and screened for malaria parasite using Malaria Ag P.f and Malaria Ag P.f/Pan kits (SD BIOLINE, Cat. No: SD05FK50 and SD05FK60 respectively). Demography information on guards were collected using structured questionnaires. Result obtained showed an overall prevalence of 17.62% Plasmodium infection among guards screened using both kits. Age, sex and season were found to significantly influence the prevalence of P. falciparum infection among guards in Kaduna metropolis (P < 0.05). It is recommended that managements of private security outfits should provide their staff with adequate protective measures against mosquito transmitted diseases for improved workers efficiency and reduce man hour loss.

Performance of SD Bioline Malaria Ag Pf/Pan rapid test in the diagnosis of malaria in South-Kivu, DR Congo.

IntroductionUse of malaria rapid diagnostic tests (RDTs) has improved the management of this disease. We evaluated the validity of the SD-Bioline Malaria-Ag-Pf/Pan™ (Batch 60952) RDT supplied by the Malaria Control Program of the DRCongo.MethodscChildren (n = 460) aged below 5 years seen in curative care (CC) for suspected malaria and in pre-school consultation (PSC) in two rural centers underwent clinical evaluation and capillary blood collection for microscopic reading of thick smear (TS) and thin film (BF), and for RDT. Sensitivity (Se), specificity (Sp), positive (PPV) and negative (NPV) predictive values of the RDT, and the corresponding accuracy and Youden indices were determined using microscopic data as reference. Results were compared using the Chi-square test.ResultsMicroscopy showed malaria infection in 53.8% of CC and in 10.8% of PSC children. Similar results were obtained using the RDT (CC: 47.1%; PSC: 18.3%; P > 0.05 vs. microscopy). Se of the RDT was 82.1%, Sp 92.0%, PPV 88.5% and NPV 87.4%. RDT positivity was significantly (p < 0.01) associated with some symptoms (chills, profuse sweating) and with a recent history of malaria attack. In addition, Se of the RDT depended on parasitemia and decreased at low parasite denstity.ConclusionSD-Bioline Malaria-Ag-Pf/Pan™ RDT has a relatively good sensitivity and specificity but seems useful only for high parasitemia. Negative SD Bioline Malaria Ag Pf/Pan™ RDT should be complemented with microscopy when clinical signs suggest malaria.

Typhoid, Malaria and their Concurrent Infections in Fondonera, West Region of Cameroon

Public health awareness of concurrent malaria and typhoid prevalence situation in poor-resource communities such as Fondonera in the West region of Cameroon is scanty. A retroprospective study was designed to determine malaria, typhoid and their association (malaria + typhoid) prevalence’s. The SD Bioline malaria Ag Pf/Pan 05FK60 rapid diagnostic test kit was used for pre-testing and Giemsa thick and thin smear staining technique was used as a confirmatory test. The widal agglutination test was used for typhoid fever diagnosis and haemoglobin concentration determined using the haemoglobin color scale method. Concurrent malaria and typhoid infection prevalence was 3.31%. Malaria prevalence (10.92%) alone was greater than typhoid prevalence (7.28%) alone. Infection prevalence for both typhoid and malaria was high in patients with haemoglobin concentration <11 g/dl (5.62%) than those with normal haemoglobin ≥11 g/dl (3.31%). Risk factors such as profession and level of education were significantly affected by the two diseases. Concurrent malaria and typhoid infection exists in the Fondonera community of West Cameroon and their presence is a call for public health concern.

DIAGNOSTIC PERFORMANCE EVALUATION OF THE SD BIOLINE MALARIA ANTIGEN AG PF/PAN TEST (05FK60) IN A MALARIA ENDEMIC AREA OF SOUTHERN ETHIOPIA.

SUMMARY Rapid diagnostic tests (RDTs) capable of detecting and differentiating Plasmodium species are needed in areas in which microscopy is unsuitable. This study was conducted to assess the diagnostic performance of the rapid test kit - SD BIOLINE Malaria Ag Pf/Pan(r) (05FK60) in an endemic area. Microscopy of Giemsa-stained blood films were performed to detect and estimate the Plasmodium density in malaria suspected patients. The performance of the SD BIOLINE Malaria Ag Pf/Pan test was evaluated using 272 Plasmodium-positive and 102 negative blood samples. The overall sensitivity of the SD BIOLINE Malaria Ag Pf/Pan test was 99.5% for P. falciparum and 92.6% for non-P. falciparum malaria infections. The respective specificity, PPV, and NPV of the test were 98.0, 98.4, and 99.0% for the diagnosis of P. falciparum, and 100.0 %, 100.0%, and 94.4% for non-P. falciparum species. The SD BIOLINE Malaria Ag Pf/Pan test showed an excellent performance in diagnosing Plasmodium infections in an endemic setting. Therefore, this point-of-care test could be used as an alternative to microscopy in places where P. falciparum is endemic and microscopy is unsuitable.

Prevalence and predictors of asymptomatic malaria parasitemia among pregnant women in the rural surroundings of Arbaminch Town, South Ethiopia.

BackgroundIn Sub-Saharan African countries, including Ethiopia, malaria in pregnancy is a major public health threat which results in significant morbidities and mortalities among pregnant women and their fetuses. In malaria endemic areas, Plasmodium infections tend to remain asymptomatic yet causing significant problems like maternal anemia, low birth weight, premature births, and still birth. This study was conducted to determine the prevalence and predictors of asymptomatic Plasmodium infection among pregnant women in the rural surroundings of Arba Minch Town, Southern Ethiopia.MethodsA community based cross-sectional study comprising multistage sampling was conducted between April and June, 2013. Socio-demographic data were collected by using a semi-structured questionnaire. Plasmodium infection was diagnosed by using Giemsa-stained blood smear microscopy and a rapid diagnostic test (SD BIOLINE Malaria Ag Pf/Pv POCT, standard diagnostics, inc., Korea).ResultsOf the total 341 pregnant women participated in this study, 9.1% (31/341) and 9.7% (33/341) were confirmed to be infected with Plasmodium species by microscopy and rapid diagnostic tests (RDTs), respectively. The geometric mean of parasite density was 2392 parasites per microliter (μl); 2275/ μl for P. falciparum and 2032/ μl for P. vivax. Parasitemia was more likely to occur in primigravidae (Adjusted odds ratio (AOR): 9.4, 95% confidence interval (CI): 4.3–60.5), secundigravidae (AOR: 6.3, 95% CI: 2.9–27.3), using insecticide treated bed net (ITN) sometimes (AOR: 3.2, 95% CI: 1.8- 57.9), not using ITN at all (AOR: 4.6, 95% CI: 1.4–14.4) compared to multigravidae and using ITN always, respectively.ConclusionAsymptomatic malaria in this study is low compared to other studies’ findings. Nevertheless, given the high risk of malaria during pregnancy, pregnant women essentially be screened for asymptomatic Plasmodium infection and be treated promptly via the antenatal care (ANC) services.

Detection and Species Identification of Malaria Parasites by Nested-PCR: Comparison with Light Microscopy and with SD BIOLINE Malaria Ag Test in Luanda, Angola

Detection and Species Identification of Malaria Parasites by Nested-PCR: Comparison with Light Microscopy and with SD BIOLINE Malaria Ag Test in Luanda, Angola

Comparative Study of Malaria Prevalence among Travellers in Nigeria (West Africa) Using Slide Microscopy and a Rapid Diagnosis Test.

Malaria is a major disease in Africa and leads to various public health problems. A study was carried out at the Aviation Medical Clinic Laboratory, Murtala Mohammed Airport, Ikeja, Lagos State, Nigeria, in 2014. The work aimed to determine the prevalence of malaria among patients attending the laboratory. Blood samples were therefore collected from 51 patients and subjected to both blood smear microscopy and a rapid immunochromatographic diagnostic test (SD BIOLINE Malaria Ag) for detection of, respectively, malaria parasites and antigens. At the end of the study, 22% of the patients were detected positive by the microscopic examination while 9.8% were tested positive when using SD BIOLINE Malaria Ag. The outcomes of the study show a high prevalence of malaria at the airport. This represents a serious risk factor leading to a high likelihood of spread and occurrence of malaria in other countries including Western countries whereby the disease is nonendemic. It also pointed out that the blood smear microscopy seems to be better than Rapid Diagnosis Test (RDT) for malaria diagnosis.

Simulation of B cell affinity maturation explains enhanced antibody cross-reactivity induced by the polyvalent malaria vaccine AMA1.

Polyvalent vaccines use a mixture of Ags representing distinct pathogen strains to induce an immune response that is cross-reactive and protective. However, such approaches often have mixed results, and it is unclear how polyvalency alters the fine specificity of the Ab response and what those consequences might be for protection. In this article, we present a coarse-grain theoretical model of B cell affinity maturation during monovalent and polyvalent vaccinations that predicts the fine specificity and cross-reactivity of the Ab response. We stochastically simulate affinity maturation using a population dynamics approach in which the host B cell repertoire is represented explicitly, and individual B cell subpopulations undergo rounds of stimulation, mutation, and differentiation. Ags contain multiple epitopes and are present in subpopulations of distinct pathogen strains, each with varying degrees of cross-reactivity at the epitope level. This epitope- and strain-specific model of affinity maturation enables us to study the composition of the polyclonal response in granular detail and identify the mechanisms driving serum specificity and cross-reactivity. We applied this approach to predict the Ab response to a polyvalent vaccine based on the highly polymorphic malaria Ag apical membrane antigen-1. Our simulations show how polyvalent apical membrane Ag-1 vaccination alters the selection pressure during affinity maturation to favor cross-reactive B cells to both conserved and strain-specific epitopes and demonstrate how a polyvalent vaccine with a small number of strains and only moderate allelic coverage may be broadly neutralizing. Our findings suggest that altered fine specificity and enhanced cross-reactivity may be a universal feature of polyvalent vaccines.

Study on validity of a rapid diagnostic test kit versus light microscopy for malaria diagnosis in Ahmedabad city, India

Light microscopy of blood smears for diagnosis of malaria in the field has several limitations, notably delays in diagnosis. This study in Ahmedabad in Gujarat State, India, evaluated the diagnostic performance of a rapid diagnostic test for malaria (SD Bioline Malaria Ag P.f/Pan) versus blood smear examination as the gold standard. All fever cases presenting at 13 urban health centres were subjected to rapid diagnostic testing and thick and thin blood smears. A total of 677 cases with fever were examined; 135 (20.0%) tested positive by rapid diagnostic test and 86 (12.7%) by blood smear. The sensitivity of the rapid diagnostic test for malaria was 98.8%, specificity was 91.5%, positive predictive value 63.0% and negative predictive value 99.8%. For detection of Plasmodium falciparum the sensitivity of rapid diagnostic test was 100% and specificity was 97.3%. The results show the acceptability of the rapid test as an alternative to light microscopy in the field setting.

Performances of SD Bioline Malaria Ag-P.F/Pan RDT for the Diagnosis of Malaria in Febrile Patients Living In Gabon, Central Africa

The SD Bioline malaria Ag- Pf/Pan performances were evaluated for malaria species detection in 215 febrile patients living in Gabon, using microscopy as gold standard. Malaria parasites were identified in 94 (43.7%) individuals by microscopy, and 104 (48.4%) patients tested positive by the RDT. The SD Bioline Ag-Pf/Pan global sensitivity was 96.8%. All the non-falciparum malaria species infections were correctly diagnosed by the rapid test. The specificity was of 89.3% and the false positive (FP) rate of 12.5%. The test sensitivity significantly increased with parasitaemia, being of 88.9% for parasite density below 100/ µL and 98.5% at density higher than 500 parasites/ µL (p<0.01). Among the patients with a negative blood smear, the proportion of FP results was 21.0% in those previously-treated with an antimalarial drug before the consultation, and 8.8% in individuals without self-medication. SD Bioline Ag-Pf/ Pan RDT represents a good alternative to microscopy for the diagnosis of Plasmodium spp infection.

High Performance of Histidine-Rich Protein 2 Based Rapid Diagnostic Tests in French Guiana are Explained by the Absence of pfhrp2 Gene Deletion in P. falciparum

BackgroundCare for malaria patients in endemic areas has been improved through the increasing use of Rapid Diagnostic Tests (RDTs). Most RDTs target the histidine-rich protein-2 antigen (PfHRP2) to detect P. falciparum, as it is abundant and shows great heat stability. However, their use in South America has been widely questioned following a recent publication that pinpoints the high prevalence of Peruvian field isolates lacking the gene encoding this protein. In the remote rural health centers of French Guiana, RDTs are the main diagnosis tools. Therefore, a study of PfHRP2 RDT performances and pfhrp2 genotyping was conducted to determine whether a replacement of the current pLDH-based kit could be considered.MethodsThe performance study compared the SD Malaria Ag test P.f/Pan® kit with the current gold standard diagnosis by microscopy. The prevalence of pfhrp2 and pfhrp3 deletions were evaluated from 221 P. falciparum isolates collected between 2009 and 2011 in French Guiana.ResultsBetween January 2010 and August 2011, 960 suspected cases of malaria were analyzed using microscopy and RDTs. The sensitivity of the SD Malaria Ag test P.f/Pan® for detection of P. falciparum was 96.8% (95% CI: 90.9–99.3), and 86.0% (95% CI: 78.9–91.5) for the detection of P. vivax. No isolates (95% CI: 0–4.5) lacking either exon of the pfhrp2 gene were identified among the 221 P. falciparum isolates analyzed, but 7.4% (95% CI: 2.8–15.4) lacked the exon 2 part of the pfhrp3 gene.ConclusionsField isolates lacking either exon of the pfhrp2 gene are absent in this western part of South America. Despite its sensibility to detect P. vivax, the SD Malaria Ag test P.f/Pan® kit is a satisfying alternative to microscopy in remote health centers, where it is difficult to provide highly skilled microscopists and to maintain the necessary equipment.